Castle of Glass is Linkin Park's sixth track from their fifth studio album, Living Things. It is released on February 1, 2013 as their forth single in physical format, and on March 22, 2013 as a digital single on iTunes. It appears as a theme song from the first-person-shooter video game Medal of Honor: Warfighter, and variations of this song appears on the soundtrack compilation in September 2012. Its working title was Cloverleaf.

"Castle of Glass" felt like the biggest game-changer. Over an almost alternative country melody, Mike Shinoda sings “Take me down to the river bend... wash the poison off my skin...show me how to be whole again.” It’s one of the most straight forward tunes that the band has done with a traditional song structure. Chester Bennington and Shinoda sing together as their voices, and desperation, rise, “I’m only a crack in this castle of glass.” [1]

Much of the record was expected and then "Castle Of Glass" ended our session. Looking over my scribbled text, I can make out “Americana” and “Bayou.” Think of it as what you love about LP and throw in a pinch of folk. With Chester’s horror movie past, we might hear this one in a spooky scene soon. As it played I could imagine youths terrified and running to the pace of the song as “…take me down to the river bend” filtered through their doom; it gave off an eerie feel. [2]

The melancholic "Castle of Glass" offers a steam-engine chug and a mountain of sound while Shinoda sings about being but a small crack in the titular edifice, illustrating belonging and futility in the same stroke. [3]

On October 10 2012, on the official YouTube channel LinkinParkTV, the music video of "Castle Of Glass" featured Medal of Honor: Warfighter is released. This version contains a slow paced intro and the beginning of the song is different from the one on the album. Some tracks were removed to accommodate the tone of the video.

"Castle of Glass" had its live debut at the VGAs 2012, where it was nominated for the Best Song in a Video Game Award. The band performed the song, but lost the award to "Cities" by Beck.

The band performed the song again on February 15, 2014 for the Music for Relief's Concert for the Philippines, making a collaboration with two members of the rock and roll band Heart (consisting of sisters Ann and Nancy Wilson) at Club Nokia in Los Angeles, California. It was premiered on AXS TV.